In recent years, studies have been performed on partial replacement of conventionally used steels with light alloys of aluminum, magnesium, or the like when structures, such as automobiles, are manufactured. For that purpose, it is necessary to perform dissimilar material joining of a light alloy and a steel.
For example, Patent Literature 1 discloses a technique in which laser brazing is used not only for joining similar materials, such as steels, but also for dissimilar material joining, e.g., of an aluminum member and a steel. Laser brazing for dissimilar material joining can be used in various applications, for example, for doors, panel members, roofs, and the like. Furthermore, Patent Literature 2 discloses a technique in which an aluminum member and a steel member are subjected to arc welding, the joining part of the aluminum alloy member is melted and joined, and the joining part of the steel member is joined by forming a thin intermetallic compound.
Examples of the shape of the weld joint of these weld joined bodies include a butt joint, a lap joint, and the like. Furthermore, from the viewpoint of assembling members and the like, a flared joint is another example of the shape of the weld joint. In automotive fenders and the like, since the appearance can be improved, it may be useful to form a structural member using a flared joint, instead of a roof rail method, in some cases. In joining the flared joint, fusion welding is generally used. For example, Patent Literature 3 discloses a technique in which laser brazing using a laser and a filler material, such as a brazing filler metal, is applied in order to suppress thermal strain during welding.